1. Field of the Invention
The present invention relates to seatbelt systems for protecting the occupant of a motor vehicle during a vehicular emergency and more particularly to seatbelt systems which also reduce the pressure felt by the occupant during the application of the seatbelt.
2. Prior Art
Generally a seatbelt system is designed to provide the seatbelt with tension so as to wind-up one end of the occupant restraining seatbelt onto a take-up device installed in the vehicle, to keep the seatbelt in close contact with the occupant during the application of the seatbelt and to wind-up most of the seatbelt after the seatbelt has been released from the use in order to prevent the scattering of the seatbelt around the vehicle.
However, the tension applied to the seatbelt affects the occupant of the vehicle by causing a feeling of pressure. The winding-up portion generating the above-described seatbelt tension is not reducible below a specified value due to the necessity for securing the winding-up of the seatbelt when the seatbelt is not in use. As a result, this tension can cause fatigue in the occupant.
Particularly, in two-door vehicles, because the shoulder seatbelt is anchored to a position relatively closer to the rear part of the vehicle, the portion of the seatbelt wound out from the take-up shaft is large and this causes an increased feeling of pressure on the occupant's shoulder.
Consequently, in the prior art various types of take-up systems designed to provided low level winding-up force in order to reduce the pressing feeling on the occupant of the vehicle after applying the seatbelt have been proposed. Of these systems, devices designed to mechanically control the seatbelt winding-up force have a drawback in that the reduced winding-up force is released and becomes a high level winding-up force when the occupant moves to some extent in the vehicle. Other devices designed to reduce the winding-up force operate through the interlock with the opening and closing operation of the door and such systems have a danger of inadvertently causing the seatbelt to be caught between the door and the vehicle body. Also, a mechanism installed in the buckle such as a switch so as to lock the take-up shaft by using a solenoid, etc., have been proposed but such systems are very expensive.